Quantum optics has proved a fertile field for experimental tests of quantum information science, from experimental verification of Bell inequality violations [Kwiat, P. G., Waks, E., White, A. G., Appelbaum, I., and Eberhard, P. H. Ultrabright source of polarization-entangled photons. Phys. Rev. A 60, R773 (1999), Tittel, W., Brendel, J., Gisin, B., Herzog, T., Zbinden, H., and Gisin, N. Experimental demonstration of quantum correlations over more than 10 km. Phys. Rev. A 57, 3229-3232 (1998)] to quantum teleportation [Bouwmeester, D., Pan, J. W., Mattle, K., Eibl, M., Weinfurter, H., and Zeilinger, A. Experimental quantum teleportation. Nature 390, 575-579 (1997), Furasawa, A., Sorensen, J. L., Braunstein, S. L., Fuchs, C. A., Kimble, H. J., and Polzik, E. S. Unconditional quantum teleportation. Science 282, 706-709 (1998)]. However, quantum optics has not thought to provide a practical path to efficient and scalable quantum computation, and most current efforts to achieve this have focussed on solid state implementations. This orthodoxy was challenged recently when Knill et al. [Knill, E., Laflamme, L., and Milburn, G. J. Efficient linear optics quantum computation. Nature 409, 46 (2001)] showed that, given single photon sources and single photon detectors, linear optics alone would suffice to implement efficient quantum computation. While this result is surprising, the complexity of the optical networks required is daunting.